AzureAutoHibernate

Automatically hibernate Azure VMs when idle, using IMDS + Managed Identity.
Runs as a lightweight Windows service with optional toast notifications.

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Downloads

Grab the latest binaries here:
https://github.com/smitstech/AzureAutoHibernate/releases

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Features

• Idle detection with configurable thresholds
• Pre-hibernate toast notification
• Hibernate via Azure IMDS using Managed Identity
• Windows service + notifier app
• No Azure credentials stored locally
• Extremely lightweight and safe

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Why?

Dev/test VMs cost money when left running.
AzureAutoHibernate shuts them down automatically when they're idle — similar to a laptop closing the lid.

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Quick Start

1. Enable Managed Identity

az vm identity assign --name YOUR_VM --resource-group YOUR_RG

2. Grant Hibernate Permission

PRINCIPAL_ID=$(az vm identity show --name YOUR_VM --resource-group YOUR_RG --query principalId -o tsv)

az role assignment create \
  --assignee $PRINCIPAL_ID \
  --role "Virtual Machine Contributor" \
  --scope "/subscriptions/YOUR_SUBSCRIPTION/resourceGroups/YOUR_RG/providers/Microsoft.Compute/virtualMachines/YOUR_VM"

3. Copy Files to VM

Place these in a folder (e.g., C:\Program Files\AzureAutoHibernate\):

• AzureAutoHibernate.exe
• AzureAutoHibernate.Notifier.exe
• AzureAutoHibernate.Updater.exe
• config.json

4. Install the Service

AzureAutoHibernate.exe -install
sc create AzureAutoHibernate binPath= "C:\Program Files\AzureAutoHibernate\AzureAutoHibernate.exe" start= auto
sc start AzureAutoHibernate

5. Verify

Open Event Viewer → Applications and Services Logs → AzureAutoHibernate

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Features

• Automatic VM Discovery via Azure IMDS

• Session Monitoring for active + disconnected users

• Keyboard/Mouse Activity Detection

• Three Idle Conditions (configurable thresholds):

  • No users logged in
  • All users disconnected
  • Logged-in user inactive

• User Warnings via toast notifications

  • Configurable warning period
  • Shows time remaining + hibernation reason
  • Cancellable via user activity

• Minimum Uptime Enforcement (prevents boot→hibernate loops)

• Azure Integration (hibernate via Managed Identity)

• Windows Service with auto-startup

• Dynamic Polling for minimal overhead

• Event Log Integration with categorized event IDs

• Flexible Logging (debug, info, warn, error)

• Auto-Update (optional, checks GitHub releases)

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Prerequisites

• Windows VM running on Azure
• VM size must support Hibernate
• System Managed Identity enabled
• Managed Identity must have the hibernate action permission
• Go 1.21+ (only required if building from source)

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Configuration

Example config.json:

{
  "noUsersIdleMinutes": 15,
  "allDisconnectedIdleMinutes": 15,
  "inactiveUserIdleMinutes": 30,
  "inactiveUserWarningMinutes": 5,
  "minimumUptimeMinutes": 5,
  "logLevel": "info",
  "autoUpdate": false,
  "updateCheckIntervalHr": 24
}

Parameters

Parameter	Description	Default
noUsersIdleMinutes	Hibernate when no users logged in	15
allDisconnectedIdleMinutes	Hibernate when all sessions disconnected	15
inactiveUserIdleMinutes	Hibernate when no input detected	30
inactiveUserWarningMinutes	Warning countdown before hibernate	5
minimumUptimeMinutes	Minimum uptime after boot/resume	5
logLevel	Logging verbosity	info
autoUpdate	Enable automatic update checking	false
updateCheckIntervalHr	Hours between update checks	24

Notes:

• At least one idle condition must be > 0
• Warning period applies only to inactive-user condition
• Auto-update downloads from GitHub releases and restarts the service automatically

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Building

Using Build Scripts (Recommended)

On Windows (PowerShell):

.\build.ps1

On Linux/Mac (with Make):

make build

Both methods automatically inject version information from git tags.

Check Version

AzureAutoHibernate.exe -version

Output:

v1.0.0

Manual Build

To build manually without version injection:

On Windows:

go build -o AzureAutoHibernate.exe ./cmd/autohibernate
go build -ldflags="-H=windowsgui" -o AzureAutoHibernate.Notifier.exe ./cmd/notifier

To cross-compile from Linux/Mac:

GOOS=windows GOARCH=amd64 go build -o AzureAutoHibernate.exe ./cmd/autohibernate
GOOS=windows GOARCH=amd64 go build -ldflags="-H=windowsgui" -o AzureAutoHibernate.Notifier.exe ./cmd/notifier

Executables:

• AzureAutoHibernate.exe — the SYSTEM Windows service
• AzureAutoHibernate.Notifier.exe — per-session notifier UI
• AzureAutoHibernate.Updater.exe — update helper (applies updates after service stops)

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Testing

Debug Mode

AzureAutoHibernate.exe -debug

Run Tests

go test ./...

View Logs

Event Viewer → AzureAutoHibernate

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Updates

Check for Updates Manually

AzureAutoHibernate.exe -check-update

This will check GitHub releases and report if a newer version is available.

Automatic Updates

Set autoUpdate: true in config.json to enable automatic updates. The service will:

1. Check for updates at the configured interval (default: every 24 hours)
2. Download new versions from GitHub releases
3. Spawn the updater helper process
4. Updater stops the service reliably (with retries and 10-minute timeout)
5. Replace executable files (config.json is merged, not replaced)
6. Restart the service automatically

Safe & Reliable:

• User settings preserved: Your config.json preferences are kept, new fields added automatically
• Fails safely: Update won't proceed if service won't stop (prevents broken updates)
• Progress logging: Updates logged to %TEMP%\AzureAutoHibernate.Updater.log
• Version verification: Check Windows Event Log after restart to confirm version

Note: The updater process runs with the same permissions as the service (SYSTEM).

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How It Works

Startup

• Loads configuration
• Retrieves VM metadata via IMDS
• Validates Managed Identity and capabilities

Dynamic Polling

• Polls infrequently when far from thresholds
• Polls every 5 seconds during warning windows

Idle Detection

• No Users → Immediate hibernate
• All Disconnected → Immediate hibernate
• Inactive User → Warning period → Hibernate

Warning Phase

• Notifier displays toast notifications
• User movement cancels countdown instantly
• Notifications throttled to once every 30 seconds

Hibernate Execution

• Gets token from IMDS
• Calls Azure Hibernate API
• VM hibernates preserving memory to disk

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Architecture

AzureAutoHibernate.exe (SYSTEM)
   ├─ IdleMonitor
   ├─ NotifierManager
   │     └─ AzureAutoHibernate.Notifier.exe (per session)
   ├─ AzureHibernateClient
   └─ UpdateChecker (optional)
         └─ AzureAutoHibernate.Updater.exe (on update)

Notifier Architecture

Service (SYSTEM) → Named Pipe (JSON) → AzureAutoHibernate.Notifier.exe (User Session)

Session-0 isolation requires this two-process design.

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Troubleshooting

Notifications Not Appearing

• Make sure Windows Notifications are enabled
• Ensure AzureAutoHibernate.Notifier.exe is present
• Confirm service runs as SYSTEM
• Check Event Log for ERROR_NOT_ALL_ASSIGNED

VM Doesn't Hibernate

• Confirm Azure Hibernate is enabled for VM size
• Check Managed Identity permissions
• Look for Azure API errors in Event Log

Service Exits Immediately

• IMDS blocked or unreachable
• VM not running in Azure

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Security Considerations

• Runs as LocalSystem to access session info
• Uses Managed Identity, no secrets stored
• Metadata retrieved at runtime via IMDS
• Access tokens never persisted
• Automatically exits if not running on Azure

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Contributing

See CONTRIBUTING.md

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License

MIT